It is planned to evaluate the specific stereochemical requirements of receptor sites for antitumor active compounds. It is proposed to prepare a variety of steroidal and polyterpenoid compounds which possess antitumor as well as other biological activities modified by substituent and by stereochemistry to have their biological activities determined. The proposed steroid research has as its basis the preparation of the antibiotic fusidic acid and its derivatives, materials related biogenetically to natural steroids. The proposed polyterpenoid research has as its basis naturally occurring antitumor compounds and materials related to aphidicolin, crassin acetate, and quadrone will be synthesized.